Projectile timer



, Sept. 1, 1942. 4 u. EGGERS 2,294,730

PROJECTILE TIMER Filed Sept. 25, 1940 Inventor Ulrich Eggers,

His Attorney Patented Sept. 1,1942

PRQJE 1;.

Ulrich ss fl' -Hermsdori,

gn r to General Electric tion or New York Application September 23, 1940, Serial No. 358,034

in w September 5, 1939 me a.

I Claim. (m|161 -1%) a My invention relates to arrangements for timing moving objects, such as projectiles.

It is an object of my invention to produce an improved, reliable and accurate timing system for measuring, indicating and recording the speed oi rapidly moving objects. Other and further ob= jects and advantages will become apparent as the description proceeds.

In accordance with my invention in its pre ferred form, I provide a pair of open-sided frames or casings through which a projectile may move in succession. Suitable light-tight closures for the open sides of the casings, such as light-impervious paper are provided and photoelectric devices are mounted within the casings so that when the projectile is fired, the coverings in first one casing and then the other are ruptured so as to admit light to the photoelectric devices and the time interval between the electrical impulses produced by the illumination of the photoelectric devices is measured to obtain the measure of the speed of the projectile.

The invention will be understood more readily from the following detailed description when considered in connection with the accompanying drawing and. those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. In the drawing Fig. 1 is a perspective view of one of the impulse producers including a casing through which a projectile may be fired and Fig. 2 is a schematic diagram of the projectile timing system showing the impulse producers in perspective. Like reference characters are utilized throughout the drawing to designate like parts.

In the arrangement illustrated by way of example in the drawing, there are two photoelectric impulse producers and I2 mounted at a predetermined distance apart along the path in which the projectile, such as a rifle bullet or shell l3, may be fired. The impulse producers and I2 comprise light-tight casings I4 each with two open sides l5 so arranged that the projectile it passes through both casings M in and out through the open sides i5. Suitable means readily punctured by the projectile I! are provided tor covering the open sides lb of the casings. For example, paper strips may be employed which may be drawn from reed rolls it down through suitable guides or slots along the edges 0! the open sides or windows I! to guiding or driving rollers I'I. Within each of the casings II but away from the path l9 0! the projectile it are mounted photoelectric tubes [9 represented schematically geous to utilise paper strips 29 and 2! which have their inner surfaces silvered, or in some other manner made emcient light reflectors.

The photoelectric tubes 99, one of which is in each of the casings it, are connected in suitable electrical circuits in such a manner as to represent the electrical connections between the photoelectric tubes l9 and the amplifiers 2 2 and 23, respectively. For producing an oscillographlc record of the instant at which the electrical impulses are produced by the amplifiers 22 and 29 ,or for indicating or recording, or measuring the time interval. between such impulses, I provide a suitable recorder or a device responsive to the time interval, represented diagrammatically by the rectangle 26. As indicated by lines-2l and 28, the output of the circuits of the amplifiers 22 and 23 are electrically connected to the input circuits of the time interval responsive device 29.

The amplifiers and relays 22 and 23 may be of any desired type, such as electronic discharge tube relays as employedin the photoelectric am plifying circuits illustrated in U. 8. Patent l,897,= 850--Cramer W. La Pierre, granted February 14, 1933 or United States Patent 2,049,376-Hertwlg and Hintze, granted July 28, 1936. The device 26 for measuring and recording the time interval between the impulses may take the form of one of the devices disclosed in Patents 2,012,837- Tear, granted August 27, 1935; 2,150,7'76-Moles, granted March 14, 1939; and 2,181,728-Greentree, granted November 28, 1939. The device 26 may be arranged to be calibrated in terms oi projectile velocity instead of thetime interval between the impulses, since the impulse producers I4 are mounted a fixed distance apart, and the speed of the projectile may readily be derived from the time interval between passage from one impulse producer to the other.

Before the projectile is fired, the open sides or windows I! are closed by thelight-impervious strips 20 and 2| so that nolight can fall upon the photoelectric tubes l9. When the projecby hidden lines in Fig. 1. It may be advantatile I9 is fired it first ruptures the strip II in one schematically by connecting lines 3|.

of the casings l4, admitting light to the interior of the casing, energizing the photoelectric cells and producing a first electrical impulse. Thereafter, the projectile ruptures the first strip in the second casing and causes a second electrical impulse to be produced. The time interval between these electrical impulses is then indicated or recorded in the manner already known in the prior art. If the tests are not to be made in daylight, or if they are to be made in foggy or overcast weather, it may be desirable to provide light sources, such as searchlights 29 for casting a light beam into the interior of the casings ll when the window-covering strips are ruptured or pierced. I R

Aftereach passage of a projectile it will, of course, be necessary to reclose the openings at the sides of'the casings, and if coverings for the windows are provided in. strip form with feed rolls mounted on the casings, the windows may be quickly recovered after each test by drawing the ends of the strips 20 and 2| down through the lower rollers H. such high speed it will tear away only the area of strip at the center portion of the windows I5 leaving the remainder of the strip intact to facilitate the operation of drawing fresh strip across the windows l5.

If desired, the windows [5 are recovered automatically after each firing of the projectile. This may be done, for example, by means of motors 30 mechanically connected to the driving rollers I1 and electrically energized by the output circuits of the amplifiers 22 and 2-3 as represented It will be understood that as soon as the light-impervious strip is ruptured admitting light to the interior of the casing, the photoelectric cell becoming illuminated causes current to flow in the amplifier 22 or 23, energizing the corresponding motor Since the projectile l 3 passes at which continues to run until the strip has been pulled down far enolfih to bring fresh strip over the casing window and prevent admission of light to the interior of the casing; thereupon the amplifler 22 or 23 is deenergized and the rotation of the motor ceases.

In accordance with the'provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof but I desire to have it understood that the app ratus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent oi the United States is:

1. A projectile timer comprising in combination, a pair of impulse producers spaced a predetermined distance apart and comprising opensided casings through which a projectile or other light is admitted to the photoelectric device only when a projectile passes through the-casing and ruptures said sheet coverings.

2. An impulse producer fora projectile timer comprising a casing having open windows on opposite sides thereof, a photoelectric device within the casing adapted to be connected to an electrical impulse producing circuit, and light-impervious sheet material covering the windows of the casing adapted to be ruptured by passage of an object through the windows of the casing.

3. An impulse producer for a projectile timer comprising a casing having open windows on opposite sides thereof. and containing a photoelectric device, feed rolls of light-impervious strip material mounted at the ends of the windows of the casing, and means for guiding the strip material from said feed rolls along the edges of the windows, whereby the strip material is adapted to be pulled across the windows to cover the same.

4. An impulse producer for a projectile timer comprising a casing having open windows on opposite sides thereof, and containing a photoelectric device, feed rolls of light-impervious strip material mounted at the ends of the windows of the casing, means for guiding the strip material from said feed rolls along the edges of the windows, whereby the strip material is adapted to be pulled across the windows to cover the same, and means for drawing the strip across the windows of the casing to remove'ruptured portions thereof and leave the windows entirely covered by unpunctured strip material.

5. An impulse producer for a projectile timer comprising a casing having open windows on opposite sides thereof, and containing a photoelectric device, feed rolls of light-impervious strip material mounted at the ends of the windows of the casing, means for guiding the strip material from said feed rolls along the edges of the windows, whereby the strip material is' adapted to be pulled across the windows to cover the same, means for drawing the strip across the windows of the casing to remove ruptured portions thereof and leave the windows entirely covered by unpunctured strip material, and electric relay means responsive to the illumination of the photo tube for energizing said strip-drawing means, whenever the photoelectric cell is illuminated.

ULRICH EGGERS. 

